Revert "[vm] Align heap allocations to 2GB regions in comp ptr mode"

This reverts commit d10d17c.

Reason for revert: Broke Mac builds

Original change's description:
> [vm] Align heap allocations to 2GB regions in comp ptr mode
>
> This only handles the POSIX case. The Windows case will work exactly the
> same as this, so I want to get this reviewed before I start porting it
> to windows.
>
> TEST=Manual testing. I'll update the unit tests once it's ported.
>
> Bug: #45059
> Change-Id: I0bc0eddd95101fc2fddfe5668488670e741af586
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/183142
> Reviewed-by: Ryan Macnak <rmacnak@google.com>
> Commit-Queue: Liam Appelbe <liama@google.com>

Bug: #45059
Change-Id: I840c31ead015f60bca32b551c8f8d31fa75ad645
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/186101
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>

runtime/vm/dart.cc

@@ -673,7 +673,6 @@ char* Dart::Cleanup() {
   IsolateGroupReloadContext::SetFileModifiedCallback(NULL);
   Service::SetEmbedderStreamCallbacks(NULL, NULL);
 #endif  // !defined(PRODUCT) && !defined(DART_PRECOMPILED_RUNTIME)
-  VirtualMemory::Cleanup();
   return NULL;
 }
 

runtime/vm/heap/pages.cc

@@ -392,11 +392,6 @@ OldPage* PageSpace::AllocateLargePage(intptr_t size, OldPage::PageType type) {
   if (page == nullptr) {
     IncreaseCapacityInWordsLocked(-page_size_in_words);
     return nullptr;
-  } else {
-    intptr_t actual_size_in_words = page->memory_->size() >> kWordSizeLog2;
-    if (actual_size_in_words != page_size_in_words) {
-      IncreaseCapacityInWordsLocked(actual_size_in_words - page_size_in_words);
-    }
   }
   if (is_exec) {
     AddExecPageLocked(page);

runtime/vm/object.cc

@@ -2499,12 +2499,8 @@ void Object::InitializeObject(uword address, intptr_t class_id, intptr_t size) {
       // If the size is greater than both kNewAllocatableSize and
       // kAllocatablePageSize, the object must have been allocated to a new
       // large page, which must already have been zero initialized by the OS.
-#if defined(DART_COMPRESSED_POINTERS)
-      needs_init = true;
-#else
       needs_init = Heap::IsAllocatableInNewSpace(size) ||
                    Heap::IsAllocatableViaFreeLists(size);
-#endif
     } else {
       initial_value = static_cast<uword>(null_);
       needs_init = true;

runtime/vm/virtual_memory.cc

@@ -19,13 +19,12 @@ void VirtualMemory::Truncate(intptr_t new_size) {
   ASSERT(new_size <= size());
   if (reserved_.size() ==
       region_.size()) {  // Don't create holes in reservation.
-    if (FreeSubSegment(reinterpret_cast<void*>(start() + new_size),
-                       size() - new_size)) {
-      reserved_.set_size(new_size);
-      if (AliasOffset() != 0) {
-        FreeSubSegment(reinterpret_cast<void*>(alias_.start() + new_size),
-                       alias_.size() - new_size);
-      }
+    FreeSubSegment(reinterpret_cast<void*>(start() + new_size),
+                   size() - new_size);
+    reserved_.set_size(new_size);
+    if (AliasOffset() != 0) {
+      FreeSubSegment(reinterpret_cast<void*>(alias_.start() + new_size),
+                     alias_.size() - new_size);
     }
   }
   region_.Subregion(region_, 0, new_size);

runtime/vm/virtual_memory.h

@@ -32,7 +32,6 @@ class VirtualMemory {
   intptr_t AliasOffset() const { return alias_.start() - region_.start(); }
 
   static void Init();
-  static void Cleanup();
 
   // Returns true if dual mapping is enabled.
   static bool DualMappingEnabled();
@@ -88,7 +87,7 @@ class VirtualMemory {
 
   // Free a sub segment. On operating systems that support it this
   // can give back the virtual memory to the system. Returns true on success.
-  static bool FreeSubSegment(void* address, intptr_t size);
+  static void FreeSubSegment(void* address, intptr_t size);
 
   // These constructors are only used internally when reserving new virtual
   // spaces. They do not reserve any virtual address space on their own.

runtime/vm/virtual_memory_fuchsia.cc

@@ -51,8 +51,6 @@ void VirtualMemory::Init() {
   page_size_ = CalculatePageSize();
 }
 
-void VirtualMemory::Cleanup() {}
-
 static void Unmap(zx_handle_t vmar, uword start, uword end) {
   ASSERT(start <= end);
   const uword size = end - start;
@@ -176,11 +174,10 @@ VirtualMemory::~VirtualMemory() {
   }
 }
 
-bool VirtualMemory::FreeSubSegment(void* address, intptr_t size) {
+void VirtualMemory::FreeSubSegment(void* address, intptr_t size) {
   const uword start = reinterpret_cast<uword>(address);
   Unmap(zx_vmar_root_self(), start, start + size);
   LOG_INFO("zx_vmar_unmap(0x%p, 0x%lx) success\n", address, size);
-  return true;
 }
 
 void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {